SACRAMENTO (CN) –Over a dozen California cities, water agencies and environmentalists sued the state late Tuesday, alleging that state regulators have been secretly plotting and discussing a contentious $16 billion water project.

The petitioners, led by Sacramento and San Joaquin counties, have uncovered public records that they claim prove that State Water Resources Board staffers discussed technical reviews and other documents regarding the California WaterFix with the project’s lead agencies.

“Evidence revealed in response to a recent request under the Public Records Act demonstrates deliberate obstruction, and possible collusion by the Department of Water Resources, U.S. Bureau of Reclamation and [water board staff],” the complaint filed in Sacramento Superior Court states.

The water board must assess and sign off on the project’s environmental review before construction can finally begin on the decades-old project. It finished the first phase of the permit review and is currently holding hearings on the project’s impact on fish and wildlife.

More than 50 cities, counties, water suppliers and environmental groups have officially opposed the state’s permit application and the WaterFix as a whole.

The project calls for two 35-mile tunnels under the Sacramento-San Joaquin River Delta. The tunnels would funnel water around the delta to the state’s southernmost farmers and cities, including Los Angeles. Gov. Jerry Brown’s administration has signed off on the project and hopes to begin construction by the end of 2018.

In their 37-page complaint, the petitioners are asking the court to prevent the water board from continuing public hearings and force it to release all evidence of off-the-record talks between water board staffers and project stakeholders.

In the latest twist of the project that has been perennially delayed by lawsuits, design changes and money shortages, someone opposing the project filed a public records request for ex parte or private communications between the department of water resources and the water board.

In response, a water board attorney released a cache of emails in Oct. 2017, detailing talks and meetings between staffers and project stakeholders. The emails show at least 12 separate instances of private talks from 2015 to 2016, with topics broaching “preparation of the final environmental impact report” to “modeling” that was eventually presented to the water board.

The records show that staffers were discussing the project privately with the stakeholders, not commissioners who vote on the subject matter.

But the water board is defending and downplaying the once-secret private meetings. It says the communications concerned technical matters and that staffers didn’t relay information to commissioners.

“Based on the evidence before us, we conclude that no off-the-record information was indirectly passed by water board staff from the department of water resources to us or to any other member of the water board,” states a letter signed by Felicia Marcus, water board chair.

The water board did not respond to an email request for comment late Tuesday. Sacramento County’s counsel Andrew Hitchings of Somach Simmons & Dunn said the staffers’ ex parte talks have tainted the public hearings. He says the petitioners have already filed a motion for a temporary restraining order and will be in court Friday morning.

Other petitioners include the cities of Antioch and Stockton, Yolo, Solano and Contra Costa counties and the California Sportfishing Protection Alliance. They are asking for a permanent injunction preventing the water board from continuing hearings until the court weighs in on the ex parte communications.

The petitioners say the ongoing water board hearings are the “most significant water rights proceedings in the history of the state of California.” Among other things, the opponents say the alleged illegal backroom talks have prevented them from receiving a “fair hearing.”

The second stage of the water board’s review is expected to last through June.